1. Field of the Invention
This invention relates to piping components for distribution and collection of fluids from grids supporting particulate material such as adsorbents or catalyst. The invention is specifically directed to fluid distributor-collector devices which are placed at several intermediate points in a cylindrical bed of solid material to allow the addition or withdrawal of a liquid stream at any of these several points.
2. Description of the Prior Art
Fluid-solids contacting apparatus are in widespread commercial use as reactors and as adsorption zones. These devices are normally cylindrical columns containing a cylindrical mass of the solid contact material. The solid contact material may be catalyst or solid adsorbent. The fluid flows through the cylindrical mass of solids along the major axis of the column and may flow from one end of the column to another or from one intermediate point in the column to another. To maximize the effectiveness of the intended operation, the fluid should have a uniform composition and flow rate at all points across the cross section of the column to establish a desired xe2x80x9cplug flowxe2x80x9d.
Pressure vessels that contain particulate material for contacting fluids such as gas or liquid process streams are standard features of the chemical and refining industries. In processes for the selective adsorption of components from a multi-component feed and in processes for multi-stage contacting of reactants with a catalyst, partitions commonly subdivide the mass of adsorbent or catalyst in the interior of the pressure vessel into different chambers. The chambers retain a series of adsorbent or catalyst beds comprising discrete particles which permit staged or multiple contacting operations within a single pressure vessel. Such arrangements are routinely used in processes for the simulated moving bed adsorption process. Some fluid-solids contacting columns, especially those used to simulate the movement of the bed of solids, have multiple fluid feed and withdrawal points located intermediate to the ends of the column. At these points it is desired to respectively disperse or collect fluid across the entire cross section of the column.
A simulated moving bed adsorbent process exemplifies a process that regularly uses multiple partitions in relatively large pressure vessels. U.S. Pat. No. 2,985,589, the contents of which are hereby incorporated by reference, describes the moving bed adsorbent process in detail. The process distributes and collects process streams from multiple chambers of adsorbent defined by internal partitions located within a pressure vessel and composed of distribution/collection grids. Periodic shifting of the input and effluent streams over the chambers simulates movement of the adsorbent and permits delivery or withdrawal of the streams with a desired concentration profile.
Delivering or withdrawing the streams requires flat distribution grids. Common arrangements dispose the grids in a vertically oriented pressure vessel having a vertical centerpipe within the vessel with the grids spaced apart vertically for horizontal fluid distribution. U.S. Pat. No. 4,378,292 shows a typical large-diameter grid arrangement. Each grid is in the form of a flat ring extending between the centerpipe and the vertical outer wall of the vessel and comprises a plurality of grid sectors or semi-annular segments that have an overall wedge shape. Beds of solid particles are located between the layers of fluid distributor grids. Grid sectors at each grid level are placed side by side to fill the annular area between the centerpipe and vessel wall.
The grids receive or collect fluid from a plurality of fluid distribution/collection manifolds located in or about the centerpipe at points intermediate the vertically adjacent layers of fluid distributor grids. Requirements for the relatively uniform collection and distribution of fluids from the grids results in the withdrawal or addition of fluid from a central portion of each grid sector. Thus piping is needed to extend from the grid sector through the bed of adsorbent material to the manifold. The term xe2x80x9cgrid pipingxe2x80x9d refers to the plurality of fluid distribution/collection pipes that extend from each fluid distributor grid sector to a manifold located above the fluid distributor grid.
Most processes need provision for periodic replacement of the particulate material in the beds which requires disassembly and re-assembly of the grids. To facilitate installation, removal, and maintenance of the grid sectors and the grid piping one or more connections are placed along the length of the grid pipes for installation and removal of the piping. Common practice uses bolted flanges to provide these detachable connections. Installing and maintaining the piping in the numerous grid sections and having the piping connections present in the adsorbent poses a number of disadvantages for the process. For example a differential pressure of as little as 2 psi or less across the relatively flat grids can structurally damage the partitions by causing permanent deformation. Structural damage to the partitions has the potential to create leaks in associated connections of the distribution/collection piping. Such leaks typically contaminate the zones created by the partition and reduce the effectiveness of the separation, particularly with respect to the purity and/or yield of the products recovered from the process.
The flanges must therefore resist leakage at the piping connections. The size and bulk of the necessary flanges detract from process operations. The volume of the flanges over and above the volume of an equivalent length of pipe displaces additional catalyst or adsorbent from the bed. Any loss of particulate material reduces the effective inventory of the bed for the process application.
More importantly, the enlarged profile of the flange relative to the piping disrupts fluid flow through the particulate material immediately upstream and downstream of the protruding flange elements. Adsorbent material downstream of the flange is particularly sensitive to the blocked flow of fluid and results in a xe2x80x9cshadowingxe2x80x9d effect that renders some portion of the downstream absorbent ineffective for separation and susceptible to extended retention times. The extended retention times further disrupt the desired plug flow of the fluid and can raise the level of impurities in the final products. The degradation of process performance from shadowing usually has the greatest impact when separating viscous materials such as fructose and glucose where the relatively high solids content liquids results being quite viscous as compared to petroleum derived streams.
A well known type of piping connection uses a series of machined grooves on the ends of pipes that are connected by bridging links that have complementary grooves for engaging the grooves on the pipe ends. A sleeve or other retaining means is used to hold the link members against the pipes and the cooperating grooves in engagement. Different forms of these types of connections can be seen in U.S. Pat. No. 5,152,556, U.S. Pat. No. 5,265,917, U.S. Pat. No. 5,131,632, and U.S. Pat. No. 4,159,132. These types of connections have not been used in applications that route piping through beds of particulate material.
Accordingly, it is an object of this invention to improve the utilization and performance of adsorbent or catalyst in partitioned beds of particulate material separated by distribution/collection grids.
It is a further object of this invention to improve the operation of simulated moving bed adsorption process by reducing flow disruption and adsorbent displacement resulting from the presence of grid piping.
It has now been discovered that low profile pipe connections can significantly improve process performance or substantially reduce reload time for partitioned beds of particulate material separated by distribution/collection grids. This invention is a multi-sectored grid arrangement that connects piping from an intermediate point on each grid sector with a central or peripheral fluid distribution point through the use of a low profile connection. The reduction in diameter of the low profile connection over flanged connections is substantial.
The low profile connection has an outer radius that is no greater than the 1.25 times inner diameter of the distribution pipe. More typically, the low profile connection provides a mechanical connection having an outer radius that is typically no greater than the inner diameter of the pipe sections that it connects. A flange for a nominal 3-inch diameter pipe has an approximate outside diameter of 8 inches, whereas a typical low profile connection for use in this invention has a diameter of only 5 inches.
When subjected to mechanical loads from partition deformation, typical low profile connections resist leakage to a greater degree than most bolted flange-type connections. Deformation of the partitions, particularly to the point of causing structural damage, results in leakage (commonly referred to as xe2x80x9copening upxe2x80x9d) of a bolted connection. The connection contemplated for use in this invention can resist such leak producing deformation to about the same extent as the piping that it connects.
The use of this apparatus and process can improve the compositional control of a process stream passing into or withdrawn from a processing chamber as well as increasing the contacting capacity of a particulate material contained in the processing chamber. For an adsorption process, compositional control and increased contacting capacity translates into higher recoveries and purities of the product streams. This invention is highly effective in beds where the invention provides a fluid-solids contacting apparatus for utilization in columns in which a vertical oriented cylindrical bed of adsorbent is divided into a large number of zones by means to admix, add or withdraw a fluid and thereby facilitate the movement of adsorption and desorption zones within the bed to simulate a moving bed of the adsorbent.
Accordingly, in one embodiment, this invention is a fluid-solids contacting apparatus that includes a cylindrical vessel having a vertical major axis and a plurality of distributor grids spaced apart vertically and extending horizontally for distribution or collection of fluid. A plurality of chambers retains solid particles between the layers of fluid distributor grids. A plurality of fluid distribution pipes extends from each grid into the chamber. Each distribution pipe has at least one mechanical connection for joining separable sections of each distribution pipe. The connection comprises a plurality of grooves defined transversely on each opposing end of the connection and a plurality of cooperating grooves defined transversely on a plurality of links for holding the connection ends in sealed alignment by engagement of grooves on each end of the connection with grooves on each link. A locking member retains engagement of grooves until the connection is broken by removal of the locking member and the links. At least a portion of each distribution pipe usually extends vertically such that at least one mechanical connection is located in the vertically extended portion of the pipe. More often, a portion of each distribution pipe will also extend horizontally and a mechanical connection is located in that horizontal portion as well.
In a more limited embodiment, this invention is a fluid-solids contacting apparatus as previously described in described in the previous embodiment that also uses a vertical centerpipe located within the vessel with each grid being in the form of a flat ring extending between the centerpipe and the vertical outer wall of the vessel. Each grid is further divided into grid sectors with a distribution pipe extending vertically upwardly from each grid sector and horizontally over to an inner radius or outer radius of the grid sector.
Additional objects, embodiments, and details of the invention are set forth in the following detailed description of the invention.